Use of 9-methylfluorene as an indicator in the titration of common group IA and group IIA organometallic reagents

9-Methylfluorene was tested as an indicator in the titration of commonly used organometallic reagents. This indicator is readily prepared in three steps from fluorenone. In THF solution the deprotonated indicator is red and exhibits a sharp endpoint. The highly basic reagents sec-butyllithium and tert-butyllithium can be titrated in ether solution, where the color of the deprotonated indicator is yellow.     

Dendron rodcoils: synthesis of novel organic hybrid structures

Convergent and divergent syntheses of novel organic hybrid structures termed dendron rodcoils (DRC) containing dendritic, rodlike, and coillike segments are described. The aryl ester dendron masked with 32 trifluoromethyl groups is prepared via a convergent approach using 5-(tert-butyldimethylsiloxy)isophthalic acid as the monomer unit. The activation of the focal point of the dendron allows for successful coupling between the dendron and the diblock rodcoil molecules synthesized separately. In another example, the dendritic block is grown via divergent strategy from the terminus of rodcoil using 3,5-bis(tert-butyldimethylsiloxy)benzoic acid as an AB(2) monomer. A combination of catalyzed esterification reactions and silyl deprotection chemistry proved to be a very efficient method for construction of these nanosized structures with unusual molecular architecture. Both synthetic strategies allowed for the preparation of DRCs with nearly monodisperse dendritic blocks as demonstrated by NMR, MALDI-TOF, and GPC measurements.     

Correlation between formation conditions and breakdown voltage of anodic oxide films on aluminum

Two series of samples were investigated: a) aluminum films with a sublayer of tantalum; b) industrial aluminum alloys AMg-2m; D16; AMc; AD-1n. The optimum composition of re-anodizing electrolyte was chosen on the basis of a solution of citric acid and ethylene glycol. The results of investigations of the sparking voltage at re-anodizing for various aluminum alloys and thicknesses of primary porous oxide are presented. The analytical dependence of breakdown voltage value on forming voltage value for alloy AD-1n was obtained. The original design of re-anodizing cell allowing increase of the sparking voltage was developed.     

Adaptive Response for Exponential Smoothing: Comparative System Analysis

In effectively applying general exponential smoothing, a central requirement is the use of a proper parameter-a proper rate of discounting past information. Since a single value for the parameter is inefficient under varying demand conditions, several methods to adjust the parameter adaptively have been developed. This paper contains an analysis and comparison of these methods.